1. Field of the Invention
The present invention relates to a heat pump equipped with an extraction heat exchanger for guaranteeing operational stability and enhancing power efficiency in the cooling mode and for supplementing a heat source in the heating mode such that the coefficient of performance is enhanced and performance in cold climates is improved, using two electronic expansion valves for controlling superheating in the heating mode, for guaranteeing a low temperature heat source, for guiding any increase in evaporation efficiency, a cycle control of the extraction heat exchanger, and relates to the structure of the extraction heat exchanger capable of being applied to the heat pump by considering uniform distribution of refrigerant and pressure decrease to change the number of tubules according to an increase in capacity of the heat pump.
2. Description of the Related Art
Since, according to the conventional art, it is very difficult to guarantee a heat source at a low-temperature side in cold climates, it is difficult to operate the heat pump due to driving loss caused by a high compression ratio and frosting, and an increase in dryness caused by the flashing of refrigerant. Generally, there are various solutions, i.e. in order to overcome the above-described problem, capacity is adjusted by an inverter, an electric heater is equipped, or insufficient heat is supplemented, and in order to overcome the high compression ratio, a two-stage compression structure is employed, or a compressor is non-conventionally machined such that a sub-cooled refrigerant is injected to an intermediate pressure zone in the compressor, and various heat exchangers are employed to improve the operational characteristics in cold climates. However, since the above methods have disadvantages of high costs and complex structure, recently, inverters and electronic expansion valves are employed to precisely adjust superheat imbalances and to increase capacity.
Moreover, although, in the case of employing the inverter, insufficient heat obtained from the low temperature heat source, i.e. short heating capacity is supplemented by increasing the frequency of the inverter in the heating mode, system efficiency is decreased.
In addition, in the heating mode, in the case of supplementing the insufficient heat via the electric heater and the overload operation by the inverter, the efficiency is decreased and a capacity changing device such as the inverter is employed so that manufacturing costs are increased. Moreover, in a conventional economizer, due to inconsistent capacity adjustment, there is the risk of vapor induction and that the superheat unbalance exceeds a predetermined valve so that the compressor may catch fire.
In particular, in a two-stage compression cycle, although two compressors are employed, or one compressor is non-conventionally machined so that the extracted refrigerant undergoes heat exchange and is injected into an intermediate pressure zone between a high pressure zone and a low pressure zone, the mass production of the non-conventional machining compressor cannot be achieved due to the non-conventional machining. Moreover, since, due to tubules, the distribution of the flow rate is not uniform, and generally precise control is very difficult when a solenoid valve is used, it is difficult to maintain uniform operation.